Oil and gas wells may be completed in a producing formation containing fines and sand which may flow with the fluids produced from the formation, whether the well is completed as an open hole or as a cased hole. The fines and sand in the produced fluids can abrade and otherwise damage completion equipment, for example seals, pump seats, rod pumps, completion tubing, and other completion equipment. To control fines and sand propagation into the completion equipment, filters (e.g., sand screens) may be installed in the completion equipment string and gravel may be packed around the screen, for example at the bottom of the wellbore.
A gravel packing completion operation may include flowing gravel laden fluid or gel down an interior of the completion string, through a gravel port, and out into a formation proximate to the wellbore. In some wells, the wellbore may be fully cased and the casing perforated. In some wells, the formation proximate to the wellbore may be fractured to enhance fluid production from the formation. The gravel laden fluid or gel may flow out through the casing perforations and into the formation, in part helping to prop the formation and enhance fluid flow, in part providing a barrier to propagation of fines and sand with fluid flow towards the completion string. The gravel packing completion operation may continue with packing gravel around the completion string screen, for example by flowing gravel laden fluid or gel down the wellbore, out a gravel port, into the annulus between the completion equipment and the wellbore and/or casing, down to the completion string screen where the gravel packs around the screen and the fluid or gel passes through the screen and up the interior of a lower portion of the completion string below the gravel port, through a cross-over port, up above a packer sealing the annulus above the packer from the annulus below the packer, and returning to surface in the annulus between the completion string and the wellbore and/or casing.
After gravel packing, non-gravel bearing fluid or gel may be reverse circulated up the interior of the completion string to remove the remaining gravel from the interior of the completion string, for example flowing non-gravel bearing fluid or gel down the annulus between the wellbore and/or casing and the exterior of the completion string, through the cross-over port, out a reverse circulate port, in the gravel port, and up the interior of the completion string. The gravel packing may be tested by determining a pressure differential across the gravel pack. In different circumstances different pressure differentials may be preferred, but in an embodiment a pressure differential of about 1000 PSI across the gravel pack and the completion screen at a standard flow rate may be deemed an indication of a successful gravel pack.